Information on Service 'CARS product query'
![[Use this service from your browser]](/static/img/usesvcbutton.png)
Further access options are discussed below
Images and data from from the CFHTLS archive research survey, a
multi-band dataset spanning 37 square degrees of sky in high galactic
latitudes.
For a list of all services and tables belonging to this service's
resource, see Information on resource 'CARS survey data'
Service Documentation
These services deliver products from the CFHTLS-Archive-Research Survey
(CARS). The survey currently offers derived products from 37
sq. degrees of the Wide part from the Canada-France-Hawaii Telescope
Legacy Survey (CFHTLS). The main documentation for the products, its
creation and its content is the publication 2009A&A...493.1197E.
Here, we discuss some points which are not evident from this publication.
AVAILABLE DATA PRODUCTS
For each 1 sq. deg. CARS pointing we currently offer the following products
(we discuss them on the example of the CARS pointing W1m0p1); a typical file
is named W1m0p1_izrgu.V1.7A.final.cat. The name contains the following
information:
- W1m0p1 -- name of CARS field under consideration
- izrgu -- filters involved in the product (here i', r', z', g', u*);
for catalogues etc. the first listed filter corresponds to
the object detection filter (here 'i'; see also 2009A&A...493.1197E)
- V1.7A -- internal CARS version number
- final -- 'final' product
The individual files we offer are:
- W1m0p1_izrgu.V1.7A.final.cat
- object catalogue in FITS binary format; beware that they are very
big and cumbersome to handle if you do not have efficient tools to
work on big FITS binary tables! (typical file size per field: 0.5GB!)
- W1m0p1_izrgu.V1.7A.final.asc.gz
- An ASCII version of W1m0p1_izrgu.V1.7A.final.cat containing a subset
of the most important catalogue quantities. This catalogue should be
sufficient for most users. The main content of the catalogue can
also be queried in the cat service.
(typical gzipped file size per field: 20MB)
- W1m0p1_izrgu.V1.7A.final.reg.gz
An ASCII ds9 region file containing saoimage/ds9 polygon entries
(in pixel coordinates). They represent the CARS image masks described
in Sect. 3.4 of 2009A&A...493.1197E. Polygons originating from different
masking procedures are encoded with different colours (look at
expressions such as '# color=yellow' at the end of each line).
We offer this file so that interested users can construct own masks
containing only parts of our global MASK key. (typical gzipped file size
per field: 1MB)
The colour coding in these files is as follows:
- yellow: masks from our object density analysis and stars identified
in the USNO-A2 catalogue
- green: stars identified in the GSC1 and GSC2 cataogues
- magenta: masks around extended haloes of bright stars
- red: masks from our asteroid track analysis
W1m0p1_irg.V1.7A.truecol.jpg
low resolution true colour i', r' and g' JPG image of the CARS field.
These images allow a quick look at the data but they are probably not
suitable for high-quality poster print-outs. (typical file size per field:
10MB)
- W1m0p1_izrgu.V1.7A.masks.obj.jpg
low resolution JPG image showing object positions and object masks
overlayed on the i'-band image. It allows a quick-look at field-layout
and object positions. (typical file size per field: 3MB)
The colour coding in this is:
- green: areas excluded from scientific analysis by our MASK key
- yellow: stellar sources (SExtractor CLASS_STAR >=0.95)
- red: galaxies with high-confidence photo-z estimates:
(SExtractor CLASS_STAR < 0.95; reliable object photometry
in five bands; BPZ ODDS quality parameter > 0.9);
see also Sect. 4 of 2009A&A...493.1197E
- blue: all other galaxies (SExtractor CLASS_STAR < 0.95)
CATALOGUE QUANTITIES
See 2009A&A...493.1197E, in particular Sect. 4, and the SExtractor Users manual
for a description of most catalogue entries. Also see the table notes.
CURRENT COVERAGE
Overview
You can access this service using:
-
form --
an interface for web browsers through an HTML form
Coverage
1.0332 3.7571 eV
This resource is not (directly) published.
This can mean that it was deemed too unimportant, for internal
use only, or is just a helper for a published service.
Equally likely, however,
it is under development, abandoned in development or otherwise
unfinished. Exercise some caution.
Other services provided on the underlying data
include:
Default Output Fields
The following fields are contained in the output by default. More
fields may be available for selection; these would be given below
in the VOTable output fields.
| Name | Table Head |
Description | Unit | UCD |
|---|
| bandpassId |
Bandpass |
Freeform name of the bandpass used
|
N/A |
instr.bandpass |
| catalogue |
Object catalogue |
FITS catalogue of objects in this field
|
N/A |
N/A |
| fieldKey |
Field |
CARS field designation
|
N/A |
meta.id |
| image |
Image data |
Access key for the data
|
N/A |
meta.ref.url |
| masklink |
JPEG masks |
Mask preview as JPEG
|
N/A |
N/A |
| ncombine |
Combined |
Number of individual frames in this stack
|
N/A |
meta.number |
| seeing |
Seeing |
Measured image seeing
|
arcsec |
instr.obsty.seeing |
| texptime |
Tot. Exposure |
Total Exposure Time
|
s |
time.duration;obs.exposure |
| truecollink |
Preview |
Preview color image made of i,r, and g band images
|
N/A |
N/A |
| weight |
Weights |
Weight FITS
|
N/A |
N/A |
VOTable Output Fields
The following fields are available in VOTable output. The verbosity
level is a number intended to represent the relative importance
of the field on a scale of 1 to 30. The services take a VERB argument.
A field is included in the output if their verbosity level is
less or equal VERB*10.
| Name | Table Head |
Description | Unit | UCD |
Verb. Level |
|---|
| accref |
Product key |
Access key for the data
|
N/A |
meta.ref.url |
1 |
| bandpassId |
Bandpass |
Freeform name of the bandpass used
|
N/A |
instr.bandpass |
10 |
| accsize |
File size |
Size of the data in bytes
|
byte |
VOX:Image_FileSize |
11 |
| ncombine |
Combined |
Number of individual frames in this stack
|
N/A |
meta.number |
15 |
| texptime |
Tot. Exposure |
Total Exposure Time
|
s |
time.duration;obs.exposure |
15 |
| fieldKey |
Field |
CARS field designation
|
N/A |
meta.id |
20 |
| magzperr |
Err. Mag. ZP |
Estimated Magnitude Zeropoint Error
|
mag |
stat.error;phot.mag;arith.zp |
20 |
| seeing |
Seeing |
Measured image seeing
|
arcsec |
instr.obsty.seeing |
20 |
| weightlink |
Weights |
Weight FITS
|
N/A |
N/A |
20 |
| weightsize |
Size(Weights) |
Size of weight FITS
|
N/A |
N/A |
20 |
| regionlink |
DS9 masks |
Image masks as DS9 regions
|
N/A |
N/A |
20 |
| regionsize |
Size(masks) |
Size of DS9 region file
|
N/A |
N/A |
20 |
| truecollink |
Preview |
Preview color image made of i,r, and g band images
|
N/A |
N/A |
20 |
| masklink |
JPEG masks |
Mask preview as JPEG
|
N/A |
N/A |
20 |
| catlink |
Object catalogue |
FITS catalogue of objects in this field
|
N/A |
N/A |
20 |
| catsize |
Size(cat.) |
Size of FITS catalogue of objects in this field
|
N/A |
N/A |
20 |
| magzp |
Mag. ZP |
AB Magnitude Zeropoint
|
mag |
phot.mag;arith.zp |
25 |
| seeingerr |
Err. Seeing |
Measured image Seeing error
|
arcsec |
stat.error;instr.obsty.seeing |
25 |
Copyright, License, Acknowledgements
If you use the CARS products for your own research,
please give proper acknowledgment to
CADC, the
CFHTLS project and the
publication 2009A&A...493.1197E
Citation Info
VOResource XML (that's something exclusively for VO nerds)
![[Operator logo]](/static/img/logo_medium.png){kind=logo}